Divers failed to recover any additional victims by early Friday evening as they searched through cars and debris submerged in the Mississippi River north of the site where Interstate 35-West collapsed in Minneapolis Wednesday.
Twelve vehicles have been found empty since the recovery mission began Thursday, Hennepin County Sheriff Rich Stanek said at an afternoon press conference.
The official death toll in the fatal I-35W bridge collapse remained at five, while one of the eight "missing" Stanek cited earlier Friday -- a number much lower than in previous reports -- had been accounted for. Still, Stanek cautioned against any using any concrete number for the missing, a count he said could continue to fluctuate.
The number of fatalities is still expected to climb as the dangerous recovery mission continues over the next several days.
Up to 20 dive boats were on the river upstream from the collapse site searching "targets" identified by sonar that may or may not be vehicles.
Visibility, at less than a foot, has complicated the search, as have the Mississippi River currents, which formed into "man-made eddies" because of the debris. Officials at the Army Corps of Engineers have been adjusting the river's water flow to try to control dive conditions, but the process has been slow because of the need to ensure the safety of the rescue workers.
Authorities also identified Minnesota resident Paul Eickstadt, 51, as the fifth confirmed fatality Friday.
Thursday evening, officials identified four Minnesota residents confirmed dead in the bridge collapse: Sherry Engebretsen, 60; Julia Blackhawk, 32; Patrick Holmes, 36; and Artemio Trinidad-Mena, 29.
Mark Rosenker, the director of the National Transportation Safety Board, said Friday afternoon that four videos provided by the Army Corps had given investigators early clues about the collapse.
"We noticed that this (southern) section of this part of the bridge seemed to behave differently in the video and in the final way it sat after the collapse," Rosenker said. "It appears it has shifted 50 feet to the east."
Rosenker said he didn't want to give the impression that investigators had the answer to the collapse, but he also called the discovery a "step forward."
"We haven't ruled anything out, anything except we believe this is an accident," he said.
President Bush is expected to visit the site of the collapse Saturday, while first lady Laura Bush toured the scene Friday.
The 500-foot span, part of I-35W, gave way shortly after 7 p.m. EDT Wednesday as slow-moving traffic crawled along the steel arch truss bridge. Some vehicles fell more than 60 feet into the river, while others ended up in awkward positions, battered by concrete and tangled in steel that exploded in all directions when the span gave way.
Federal officials alerted states Thursday night to immediately inspect all steel deck truss bridges within their borders — a total of more than 750 bridges across the country.
Officials in several states had previously said that they planned to reinspect their bridges in light of the collapse, and in Minnesota they had already began inspecting their bridges.
In 2005, the federal government rated the Minnesota bridge as "structurally deficient," a status that does not require that a bridge be closed or replaced.
"We know that the bridge was inspected in 2005 and 2006 by state inspectors, and while there was some stress and surface concerns noted, they didn't identify a need for the bridge to be replaced," said Minnesota Gov. Tim Pawlenty.
Last year's engineering report identified 52 areas of the bridge where a fracture would be considered very alarming, including some hard to inspect areas. The recommendation was that steel plates be added to critical areas.
But state officials wanted other options -- and chose the closer inspections of the 52 sections of the bridge. They defended that choice today.
"In the bridge we just had collapse, my daughter drives that bridge twice a day. if you really believe that any of us would compromise the safety of the motoring public you're in the wrong place, because we would not," said Carol Molnau, Commissioner of Transportation.
More than 73,000 bridges were rated as "structurally deficient" in 2006, while an additional 80,000 were considered "functionally obsolete," according to federal transportation statistics.
The status does not mean a bridge is unsafe to use, Peters said at a news conference in Minneapolis Thursday. Peters also said that the federal government would immediately offer $5 million to the recovery effort and would supplant those funds as necessary.
Dan Dorgan, the director of bridges for the Minnesota Department of Transportation, laid out some of the structure's history that had earned the bridge its "structurally deficient" status. He cited reports over the last 20 years that had found bearing and corrosion problems and fatigue cracks that were repaired in the early 1990s. Despite the federal designation, which a federal highway transportation official described as "programmatic," the bridge was still deemed fit for travel, Dorgan said.
According to the National Bridge Inventory on the Department of Transportation's Web site, the deck of the bridge was in fair condition, the superstructure was satisfactory and the bridge rating indicated it met currently acceptable standards. Pawlenty said Wednesday night that the bridge, built in 1967, was not expected to be replaced until 2020.
Although officials could not offer a cause of the collapse, Department of Homeland Security officials quickly ruled out any apparent terrorism. There was a construction crew on the bridge doing a resurfacing job that pared traffic from eight lanes to four, but it's not clear if the work had anything to do with the collapse. The $9 million project was a combination of $6.5 million in surface repair work and $2.5 million in related bridge work, including construction on the bridge joints.
Pawlenty announced Thursday afternoon that the state would conduct its own investigation into the collapse, concurrent with the federal probe, that would also look at all bridges throughout the state.
"A bridge in America shouldn't just fall down," Minnesota Sen. Amy Klobuchar said at the news conference. She added that the collapse is a reminder that the nation's infrastructure needs to become a funding priority.
Senate Majority Leader Harry Reid, D-Nev., said the Minnesota bridge tragedy is a wake-up call on America's deteriorating infrastructure. "Since 9/11, we have taken our eye off the ball," said Reid, suggesting that infrastructure spending has taken a back seat to spending on the war in Iraq and Afghanistan.
White House press secretary Tony Snow said Thursday morning that while the deficiency status may not mean a bridge needs to be replaced, it is up to an individual state to deal with aging infrastructure.
"This doesn't mean there was a risk of failure, but if an inspection report identifies deficiencies, the state is responsible for taking corrective actions," Snow said.
President Bush also addressed the collapse and offered condolences but jumped off those sentiments to implore Congress to pass critical spending bills that would address some of the nation's infrastructure deficiencies before breaking for the August recess.
Many survivors compared the collapse and subsequent wreckage to an earthquake or the Sept. 11 terrorist attacks.
Nevada Torrance, of Duluth, Minn., was driving in his car with his family when the 40-year-old bridge began to go. "It was a matter of two or three drops," Torrance told ABC News. "We would drop and then pause, drop and then pause."
Lynn Luban was captured on the Army Corps of Engineers video running from the collapsing bridge. She immediately called 911 and said the sound of the structure crashing into the river was enormous. "I've never heard that sound," she said. "I'd equate it to a train or a tornado or something."
Among the vehicles that safely came to rest on a collapsed section of the bridge was a school bus filled with children. They were seen exiting the rear of the bus; none of the children were seriously hurt.
The Coast Guard halted boat traffic on the Mississippi River Wednesday night for five miles to the north and south of the collapse.
Families have gathered at the Minneapolis Holiday Inn hoping for word on missing relatives or friends. At least six families were at the hotel this morning, according to officials, while others have reached out to authorities regarding missing loved ones.
The bridge, the state's most heavily trafficked, carries more than 100,000 vehicles each day and sits 64 feet above the river's surface, according to Chris Krueger, a spokesman for the Department of Public Safety.
At least 79 people were taken to area hospitals for treatment.
ABC News staff and The Associated Press contributed to this report.